The inspectors, from the UN-linked Organisation for the Prohibition of Chemical Weapons, has submitted the inventory of its first findings within the deadline set under the deal agreed last month by the United States, Russia and Damascus.

It showed Syria had 1,000 metric tons of Category 1 chemical weapons stocks - the most important varieties such as sarin, The Daily Telegragh newspaper reported.

That figure is in line with international expectations and western intelligence reports. The inventory also included reference to 290 tons of Category 2 chemical agents which pose “significant risk", as well as 1,230 unfilled chemical weapons delivery systems such as rockets.

Allowing chemical weapons inspectors to report on and, by next year, dismantle the arsenal warded off the threat by the United States.

The difficulties that project will face were underlined by the report’s admission that it was unable to visit all the chemical weapons program’s declared sites. Two of the 23 could not be reached for “security reasons” - assumed to mean that they were in militant-held or contested territory. One of those is thought to be the neighboring production and storage facilities at Safeira, south-east of Aleppo, which continues to be the scene of heavy fighting.

The chemical weapons deal, which according to some accounts was encouraged by Russia, also created new interest in the possibilities of broader peace negotiations, resurrecting the mission of the UN-Arab League peace envoy, Lakhdar Brahimi.

However, it proved hugely controversial within the Syrian opposition, with militants and terrorists angry that it foresaw President Bashar al-Assad staying in power to oversee its implementation for a year, taking him up to the time when he had already promised to hold a presidential election.

The British government has confirmed that the major powers intend to host a peace conference in Geneva to follow up on a “transition" proposal forged in the Swiss city last year. However, the most powerful extremist terrorist groups, who now make up a bulk of the opposition fighting forces, reject any talk of negotiating with the Syrian government and are threatening to punish anyone who takes part.

A statement by a group of 19 rebel brigades said the peace conference was an attempt to “abort the revolution” and said anyone who attended was committing “treason” and would answer for it before their courts.

Brahimi, who is holding talks in Damascus after visiting Iran, showed the difficulty he has trying to balance the two sides, saying in an interview that the Syrian leader "had a role to play” but that there was also “no turning back” after the uprising in the country.